On Fri, 4 Feb 2011, Giuseppe Vittucci wrote: You just have to move the nulldata command outside of the loop. 1) Load data into matrix X0 for resampling, create matrix X1 with N rows to hold resampled values 2) nulldata N --preserve 3) loop: refill random vector and put selected blocks from X0 into X1; and if you need the values as series, copy them out from the columns of X1 Allin Cottrell